{"id":1187,"date":"2015-02-06T17:09:08","date_gmt":"2015-02-06T16:09:08","guid":{"rendered":"http:\/\/www.edy.es\/dev\/?p=1187"},"modified":"2017-02-16T10:51:04","modified_gmt":"2017-02-16T09:51:04","slug":"engine-clutch-and-gearbox-in-vehicle-physics-pro","status":"publish","type":"post","link":"https:\/\/www.edy.es\/dev\/2015\/02\/engine-clutch-and-gearbox-in-vehicle-physics-pro\/","title":{"rendered":"Engine, clutch and gearbox in Vehicle Physics Pro"},"content":{"rendered":"<p>Introducing the\u00a0key components of a vehicle&#8217;s transmission that are simulated\u00a0in my upcoming vehicle physics system, Vehicle Physics Pro for Unity 3D.<\/p>\n<h2>Engine<\/h2>\n<p><a href=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/EngineInspector.png\"><img loading=\"lazy\" decoding=\"async\" class=\" size-medium wp-image-1234 alignright\" src=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/EngineInspector-144x300.png\" alt=\"EngineInspector\" width=\"144\" height=\"300\" srcset=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/EngineInspector-144x300.png 144w, https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/EngineInspector.png 382w\" sizes=\"auto, (max-width: 144px) 100vw, 144px\" \/><\/a>The engine curve was briefly introduced <a title=\"Early preview of Vehicle Physics Pro\" href=\"https:\/\/www.edy.es\/dev\/2014\/11\/early-preview-of-vehicle-physics-pro\/\">in a previous post<\/a>. Now I&#8217;ll describe the actual features and working modes of the Engine component.<\/p>\n<p><strong>The basis<\/strong> is simple: when throttle is applied the engine produces torque according to the actual rpms and the torque curve. When no throttle is applied, the engine produces brake\u00a0torque only.<\/p>\n<p><strong>The torque curve<\/strong> can be easily configured out of real data by directly configuring specific torque and rpm points in the inspector. Then adjusting the friction values makes the curve to match the shape and specs of the real one. The power curve is calculated out of the torque\u00a0curve.<\/p>\n<p>A\u00a0tricky\u00a0point not always noticed is keeping the engine powered\u00a0while\u00a0idle (that is, compensating the friction at the idle rpms), then\u00a0combining idle with throttle when applied. The engine component can\u00a0simulate this in two ways:<\/p>\n<ul>\n<li><strong>Passive:<\/strong> The engine always produces a\u00a0minimum power that counteracts the engine friction\u00a0at idle rpm. This minimum power is generated\u00a0even without throttle applied, i.e. in engine-brake mode. This mode is typical in the carburetor-based cars. They can be easily stalled if releasing the clutch with not enough throttle\u00a0applied.<\/li>\n<li><strong>Active:<\/strong> Vehicle&#8217;s electronics automatically apply the necessary power for keeping the idle rpm. This power is applied when the rpms are below the idle value. In engine-brake mode no power is being applied at all. For instance, the high-torque diesel\u00a0engines combined with the electronics keeping the idle rpm makes these vehicles harder to stall. They can even climb steep roads with the engine at idle, without throttle being applied.<\/li>\n<\/ul>\n<h4>Rev limiter<\/h4>\n<p>Despite the physical rpm limits of the engine\u00a0described by its power\u00a0curve, the engine can also be set up to cut the power above certain rpm to protect the mechanical parts.<\/p>\n<h4>Stall and startup<\/h4>\n<p>The engine can be configured to stall under realistic conditions, or not to stall at all. The power\u00a0and friction\u00a0curves are properly defined at all stages and can be configured for making the vehicle harder or easier to stall.<\/p>\n<p>Ignition key and startup engine are both simulated. A parameter &#8220;starter reliability&#8221; defines how likely the engine will be able to start or not. This parameter\u00a0may\u00a0be used for simulating parameters like external temperature, battery level, etc.<\/p>\n<p>The engine provides extra friction when stalled. If the car is moving while stalled the engine can be ignited again by releasing the clutch with a proper gear engaged, just like in reality.<\/p>\n<h2>Clutch<\/h2>\n<p><a href=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/ClutchInspector.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-medium wp-image-1237\" src=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/ClutchInspector-300x156.png\" alt=\"ClutchInspector\" width=\"300\" height=\"156\" srcset=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/ClutchInspector-300x156.png 300w, https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/ClutchInspector.png 382w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a>This component has been surprisingly simple to implement in my vehicle simulation model. Several different working modes are provided:<\/p>\n<ul>\n<li><strong>Lock ratio:<\/strong> a fictitious but simple to use clutch, where 0.0 is disengaged (transmission open) and 1.0 is engaged (locked). Any value in between provides proportional lock ratio. The actual amount of torque transfered depends on both lock ratio and engine torque.<\/li>\n<li><strong>Clutch pack:<\/strong>\u00a0this is the realistic clutch. It provides friction torque progressively up to a maximum amount. The clutch pack transfers a constant amount of torque for a given clutch pedal position, regardless of the actual torque provided for the engine. As bonus feature, clutch wear can\u00a0be easily accounted\u00a0by lowering the\u00a0maximum torque transfer value, so the component could even simulate\u00a0clutch slipping accurately.<\/li>\n<li><strong>Torque converter:<\/strong>\u00a0a fluid coupling that provides smooth and progressive lock\u00a0based on the rotational speed at both ends. Typically used in automatic transmissions. However it\u00a0can greatly improve the gameplay when used with manual transmissions, as the user doesn&#8217;t have to worry about clutch.<\/li>\n<\/ul>\n<h2>Gearbox<\/h2>\n<p>The gearbox actually defines\u00a0the type of the\u00a0transmission for the vehicle.\u00a0Most vehicle simulations implement\u00a0&#8220;automatic transmissions&#8221; as &#8220;manual gearbox with auto-shift&#8221;.\u00a0Vehicle Physics Pro simulates a true\u00a0automatic transmission with the realistic effects of smooth gear\u00a0shifting. Even changing from forward to reverse is performed\u00a0in a perfectly smooth transition.<\/p>\n<p><a href=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/GearboxAutomaticInspector.png\"><img loading=\"lazy\" decoding=\"async\" class=\" size-medium wp-image-1240 aligncenter\" src=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/GearboxAutomaticInspector-300x249.png\" alt=\"GearboxAutomaticInspector\" width=\"300\" height=\"249\" srcset=\"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/GearboxAutomaticInspector-300x249.png 300w, https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/GearboxAutomaticInspector.png 427w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p>Supported transmission\u00a0types:<\/p>\n<ul>\n<li><strong>Manual\u00a0transmission:<\/strong> gearbox engages each gear by demand.<\/li>\n<li><strong>Manual\u00a0transmission with auto-shift:<\/strong> a manual transmission where appropriate\u00a0gears are automatically engaged according to the configured\u00a0rpm values.<\/li>\n<li><strong>Automatic transmission:<\/strong> a complex\u00a0mechanism that engages the gears by applying clutches on a planetary gear system. Provides\u00a0smooth continuous transitions when shifting gears.<\/li>\n<li><strong>Semi-automatic transmission:<\/strong>\u00a0An automatic transmission in Manual mode where\u00a0gears are shifted manually in sequence. Most\u00a0cars with automatic transmission also provide a semi-automatic mode.<\/li>\n<\/ul>\n<h2>More information<\/h2>\n<p>The documentation site is live: <a href=\"http:\/\/vehiclephysics.com\">http:\/\/vehiclephysics.com<\/a>. I&#8217;m writing it as I develop the package. The development roadmap is available at the front page.<\/p>\n<p>The twitter <a href=\"https:\/\/twitter.com\/VehiclePhysics\">@VehiclePhysics<\/a> has frequently updated information and screenshots on the development progress.<\/p>\n<p>You can find a lot of interesting under-the-hood information on Vehicle Physics Pro here:<\/p>\n<p><a href=\"http:\/\/vehiclephysics.com\/advanced\/misc-topics-explained\">http:\/\/vehiclephysics.com\/advanced\/misc-topics-explained<\/a><\/p>\n<p>Interested on testing Vehicle Physics Pro even at its Alpha state? I&#8217;m opening Early Access with the Professional License add-on ($200). Check out the <a href=\"http:\/\/vehiclephysics.com\/#licensing\">licensing section<\/a> for more information.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Introducing the\u00a0key components of a vehicle&#8217;s transmission that are simulated\u00a0in my upcoming vehicle physics system, Vehicle Physics Pro for Unity 3D. Engine The engine curve was briefly introduced in a previous post. Now I&#8217;ll describe the actual features and working modes of the Engine component. The basis is simple: when throttle is applied the engine [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":1241,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":true,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[11,17,4,5],"tags":[],"class_list":["post-1187","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-slideshow","category-unity","category-vehicle-physics"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.edy.es\/dev\/wp-content\/uploads\/2015\/02\/EngineCurves.png","jetpack_shortlink":"https:\/\/wp.me\/p1PjRF-j9","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/posts\/1187","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/comments?post=1187"}],"version-history":[{"count":9,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/posts\/1187\/revisions"}],"predecessor-version":[{"id":1242,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/posts\/1187\/revisions\/1242"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/media\/1241"}],"wp:attachment":[{"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/media?parent=1187"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/categories?post=1187"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.edy.es\/dev\/wp-json\/wp\/v2\/tags?post=1187"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}